I used to work with a guy who had lost an arm in a motorbike accident, and we were always making jokes about him being "'armless", etc. He used to joke about his disability himself and would do things like creep up behing you, remove his artificial arm and thrust it in front of you with his real hand, saying "Do you want a hand with that?" (etc.)

A blind guy I know is always making jokes himself about his blindness, and is happy if someone (at least, among his friends) jokes about it too.

Most people I know with some sort of disability would prefer their friends to make light of it, rather than be afraid to say anything for fear of offending the PC brigade.

But I guess there will be exceptions. I hope my remarks above haven't offended anyone here - that wasn't my intention.